One-Step Oxide Bath for Improving Adhesion of Polymeric Materials to Metal Substrates

ABSTRACT

An oxide coating composition and a process for enhancing adhesion between a metal conducting layer and an in organic material or polymeric resin material using the oxide coating composition. The process includes the steps of applying the oxide coating composition to the metal conducting layer and bonding the inorganic material or polymeric resin material to the metal conducting layer. The oxide coating composition comprises (a) an alkali; (b) an oxidizing agent; (c) an acid; and (d) a corrosion inhibitor comprising a nitrogen heterocyclic compound;

FIELD OF THE INVENTION

The present invention relates generally to an oxide coating compositionand a method of using the same to improve adhesion of metal surfaces,such as copper, to an inorganic material or polymeric resin material, inthe manufacture of multilayer circuit boards.

BACKGROUND OF THE INVENTION

A multilayer circuit board comprises, among other things, a number ofmetal layers circuit patterns, and a number of insulating layersthere~between. These respective layers can have a wide variety ofthickness. For example, they can be on the order of only microns thick,or much thicker.

In the typical fabrication of a multilayer circuit board, patternedcircuitry innerlayers are first prepared by a process in which a copperfoil-clad dielectric substrate material is patterned with resist in thepositive image of the desired circuitry pattern, followed by etchingaway of the exposed copper. Upon removal of the resist, there remainsthe desired copper circuitry pattern.

One or more circuitry inner layers of any particular type or types ofcircuitry pattern, as well as circuitry innerlayers which mightconstitute ground planes and power planes, are assembled into amultilayer circuit by interposing one or more partially-cured dielectricsubstrate material layers (so-called “pre-preg” layers) between thecircuitry innerlayers to form a composite of alternating circuitryinnerlayers and dielectric substrate material. The composite is thensubjected to heat and pressure to cure the partially-cured substratematerial and achieve bonding of circuitry innerlayers thereto. The curedcomposite will then have a number of through-holes drilled therethrough,which are then metallized to provide a means for conductivelyinterconnecting all circuitry layers. In the course of the through-holemetallizing process, desired circuitry patterns will typically be formedon the outer-facing layers of the multilayer composite.

An alternate approach to the formation of a multilayer printed circuitboard is through additive or surface iarniner circuitry techniques.These techniques begin with a non-conductive substrate, upon which thecircuit elements are additively plated. Further layers are achieved byrepeatedly applying an imageable coating upon the circuitry and platingfurther circuit elements upon the imageable coating.

It has long been known that the strength of the adhesive bond formedbetween the copper metal of the circuitry inner layers and the curedpre-preg layers, or other non-conductive coatings, in contact therewithcan be problematic, with the result that the cured multilayer compositeor the coating is susceptible to delamination in subsequent processingand/or use. Based thereon, it is desirable to enhance the adhesionbetween the conducting and insulating layers to avoid delamination insubsequent manufacturing operations or in service. So called “blackoxide” processes have been used for years to create a strongly adherentcopper oxide layer to which an insulating layer would better adhere.

The assembled and cured multilayer circuit composite is provided withthrough-holes which require metallization in order to serve as a meansfor conductive interconnection of the circuitry layers of the circuit.The metallizing of the through-holes involves steps of resin desmearingof the hole surfaces, catalytic activation, electroless copperdepositing, electrolytic copper depositing, and the like. Many of theseprocess steps involve the use of media, such as acids, which are capableof dissolving the copper oxide adhesion promoter coating on thecircuitry innerlayer portions exposed at or near the through hole. Thislocalized dissolution of the copper oxide, which is evidenced byformation around the through-hole of a pink ring or halo (owing to thepink color of the underlying copper metal thereby exposed), can in turnlead to localized delamination in the multilayer circuit.

The art is well aware of this “pink ring” phenomenon and has expendedextensive effort in seeking to arrive at a multilayer printed circuitfabrication process which is not susceptible to such localizeddelamination.

A major problem with the current use of oxide alternative compositionsis the overall etch rate of the process. Etch rates in excess of 0.5-1.5microns (20-60 microinches) generally create too much topography on thecopper substrate. While this is advantageous for innerlayer bondingadhesion, it is unacceptable for the high-speed applications in theprinted circuit board (PCB) market.

It has been found that traditional roughened copper surfaces createsignificant signal loss at these higher frequencies. Furthermore, withthe move towards 5G technology, the market is in need of low-roughnessinnerlayer bonding applications.

Based thereon it is desirable to provide an improved low-roughnessinnerlayer bonding process that overcomes the deficiencies of the priorart.

The present invention relates generally to a nano oxide coatingcomposition that exhibits low-roughness and promotes innerlayer bondingby creating a nano crystalline oxide structure on the copper surface.

Other low-roughness technologies that have been suggested include a tinprocess (a commercial product of which is available under the trade nameFlatBond GT from Uyemura International Corporation), an organic coating( a commercial product of which is available under the trade name GLiCAPfrom Shikoku Chemicals), and an oxide technology (a commercial productof which is available under the trade name NovaBond from Atotech).

However, these technologies have some deficiencies that it would bedesirable to overcome. For example, the FlatBond GT product requiresnew, expensive equipment and the cost of tin is much higher than theoxide used in the instant invention. The GLiCAP product has been shownto exhibit poor adhesion after thermal process. Finally, the NovaBondoxide operates at a very high temperature and can only run in verticalapplications. The NovaBond oxide process also requires additionalprocess steps for the post dip application,

Thus, it would be desirable to develop an improved new process forimproving adhesion of inorganic materials to metal surfaces thatexhibits low-roughness that overcomes the deficiencies of the prior art.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved processfor the adhesion of inorganic materials to metal surfaces.

It is another object of the present invention to provide a process forthe adhesion of inorganic materials that does not require a post dipstep to ensure acid resistance.

It is another object of the present invention to provide a process thatimproves adhesion without etching the surface of the metal substrate.

It is still another object of the present invention to provide a processof promoting innerlayer bonding without etching the copper substrate,

It is yet another object of the present invention to provide a processof promoting innerlayer bonding by creating a nano crystalline oxidestructure on a copper substrate.

It is still another object of the present invention to provide animproved adhesion promoting process that can be installed in existingequipment.

It is still another object of the present invention to provide animproved adhesion promoting process that can be used at a loweroperating temperature.

To that end, in one embodiment, the present invention generally relatesto a process for enhancing adhesion between a metal conducting layer andan inorganic material or polymeric resin material during manufacture ofa multilayer circuit board, the process comprising the steps of:

-   a) optionally, applying a pre-dip to the metal conducting layer;-   b) applying an oxide coating composition to the metal conducting    layer to produce an acid resistant surface, wherein the oxide    coating composition comprises:    -   i. an alkali;    -   ii. an oxidizing agent;    -   iii. an acid; and    -   iv. a corrosion inhibitor; and-   C.) bonding the inorganic material or polymeric resin material to    the metal conducting layer.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will now be described with reference to thefollowing figures, in which:

FIG. 1 depicts the results of cosmetics and peel strength for testsamples treated in several different oxide coating compositions preparedin accordance with Example 1.

FIG. 2 depicts the results of a study to determine number of cycles todelamination for test samples treated with the several different oxidecoating compositions in accordance with Example 1,

FIG. 3 depicts the results of a delamination test for test samplestreated with the several different oxide coating compositions inaccordance with Example 1,

FIG. 4 depicts a scatterplot of edge attack versus oxide weight by bathmakeup of the oxide coating compositions of Example 1.

FIG. 5 depicts the results of a dwell time study for edge attack fortest samples treated in oxide coating compositions in accordance withExample 7.

FIG. 6 depicts the results of a dwell time study for edge attack fortest samples treated in oxide coating compositions in accordance withExample 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates generally to a process for improving theadhesion of inorganic materials and polymeric resin materials to a metalsurface, especially copper or copper alloy surfaces. The processproposed herein is particularly useful in the production of multilayerprinted circuits. The process proposed herein provides optimum adhesionbetween metallic and polymeric surfaces (i.e., the circuitry and theintermediate insulating layer), and eliminates and/or substantiallyminimizes pink ring.

The inventors of the present invention have discovered a nano-oxideprocess that exhibits low-roughness and does not require a post dip stepto ensure acid resistance. The novel one-step oxide bath describedherein also allows the process to be installed into existing oxidealternative equipment.

This novel nano oxide process does not require a post dip step to ensureacid resistance (i.e., elimination and/or minimization of “pink ring”).The one-step bath allows for the chemistry to be installed into existingoxide alternative equipment, including horizontal equipment. Inaddition, the lower operating temperature afforded by the process allowsthe one-step bath to be implemented into existing equipment.

As used herein, “a,” “an,” and “the” refer to both singular and pluralreferents unless the context clearly dictates otherwise.

As used herein, the term “about” refers to a measurable value such as aparameter, an amount, a temporal duration, and the like and is meant toinclude variations of +/-15% or less, preferably variations of +/- 10%or less, more preferably variations of +/- 5% or less, even morepreferably variations of +/-1% or less, and still more preferablyvariations of +/-0.1% or less of and from the particularly recitedvalue, in so far as such variations are appropriate to perform in theinvention described herein. Furthermore, it is also to be understoodthat the value to which the modifier “about” refers is itselfspecifically disclosed herein.

As used herein, spatially relative terms, such as “beneath,” “below,”“lower,” “above,” “upper” and the like, are used for ease of descriptionto describe one element or feature’s relationship to another element(s)of feature(s) as illustrated in the figures. It is further understoodthat the terms “front” and “back” are not intended to be limiting andare intended to be interchangeable where appropriate.

As used herein, the terms “comprises” and/or “comprising,” specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

As used herein, the term “substantially free” or “essentially free” ifnot otherwise defined herein for a particular element or compound meansthat a given element or compound is not detectable by ordinaryanalytical means that are well known to those skilled in the art ofmetal plating for bath analysis. Such methods typically include atomicabsorption spectrometry, titration, UV-V is analysis, secondary ion massspectrometry, and other commonly available analytically techniques.

All amounts are percent by weight unless otherwise noted. All numericalranges are inclusive and combinable in any order except where it islogical that such numerical ranges are constrained to add up to 100%,

The terms “composition” and “bath” and “solution” are usedinterchangeably throughout this specification.

The term “alkyl,” unless otherwise described in the specification ashaving substituent groups, means an organic chemical group composed ofonly carbon and hydrogen and having a general formula: C_(n)H_(2n+1).

The term “average” is equivalent to the mean value of a sample.

In one embodiment, the present invention generally relates to a processfor enhancing adhesion between a metal conducting layer and an inorganicmaterial or polymeric resin material, the process comprising the stepsof:

-   a) optionally, applying a pre-dip to the metal conducting layer:-   b) applying an oxide coating composition to the metal conducting    layer to produce an acid resistant surface, wherein the oxide    coating composition comprises:    -   i. an alkali;    -   ii. an oxidizing agent;    -   iii. an acid; and    -   iv. a corrosion inhibitor; and-   c) bonding the inorganic material or polymeric resin material to the    metal conducting layer.

In one embodiment, the metal conducting layer comprises copper or acopper alloy.

The method described herein is capable of treating smooth coppersurfaces to produce a nano oxide crystalline oxide structure thereonwithout having any measurable effect on surface roughness. The nanooxide crystalline oxide structure of the treated copper surface exhibitsexcellent adhesion and thermal resistance when used with variousinorganic materials and polymeric resin materials, including pre-pregmaterials. These inorganic materials include, for example, silicons,ceramics, inorganic materials used as fillers, and glass.

Examples of the polymeric resin materials include: an acrylate resin, anepoxy resin, a polyimide resin, a bismaleimide resin, a maleimide resin,a cyanate resin, a polyphenylene ether resin, a polyphenylene oxideresin, an olefin resin, a fluorine-containing resin, a polyetherimideresin, a polyether ether ketone resin, and a liquid crystal resin, andmay be a combination thereof by mixing or modifying with each other.

Exemplary polymeric resin materials include multifunctional resinsystems, including those that are designed for multilayer printed wiringboard applications that require high thermal performance andreliability. Examples of these resin systems include, for example, an370HR epoxy laminate available from Isola, Megtron Series dielectriccircuit board materials available from Panasonic, Inc. (including, forexample, Megtron M, Megtron 2, Megtron 4, Megtron 6, Megtron 7, andMegtron 7N), 6 and Megtron 7N, and microfilms such as Ajinomoto Build-upFilm (ABF), available from Ajinomoto Group.

In one embodiment, the copper surface is treated to pre-clean the coppersurface prior to contact with the oxide coating composition. Onesuitable pre-cleaner is an acid precleaner, commercial products of whichare available under the tradenames 717 Acid Cleaner, MultiBond AcidCleaner S and M-Speed Clean from MacDermid Enthone, Inc.

Thereafter, the copper surface is subjected to a pre-dip step. Thepre-dip composition is generally selected to be compatible with theoxide coating composition. In one embodiment, the pre-dip compositioncomprises the same alkali and acid as the adhesion promotingcomposition, without the organic component (i.e., corrosion inhibitor)or the oxidizing agent. The main function of the pre-dip is to seed thecopper surface with a thin layer of oxide so that the main oxide coatingbath can initiate oxide uniformly and more quickly. In one embodiment,the pre-dip is performed using a different concentration of the oxidecoating composition described herein.

In one embodiment, the metal conducting layer is contacted with thepre-dip composition for a period of about 10 to about 240 seconds, morepreferably about 30 to about 45 seconds, and is thereafter contactedwith the oxide coating composition for a period of about 10 to about 240seconds, more preferably about 30 to about 90 second, more preferablyabout 45 to about 60 seconds to produce the nano oxide crystalline oxidestructure on the surface of the metal conducting layer.

Contact with the oxide coating composition may be by any conventionalmeans, including immersion in a bath of the oxide coating composition orother means of contact for the period of time.

In an alternate embodiment, the process described herein does notrequire a pre-dip step prior to the adhesion promoting step. That is,the metal conducting layer is contacted directly with the oxide coatingcomposition without first contacting the metal conducting layer with apre-dip composition.

It has been found that the improved process of the invention results inno increased topography of the copper surface substrate, improvescosmetic appearance, and improves thermal and chemical resistance topost lamination processes. The method can be incorporated in printedcircuit board manufacturing processes to improve bonding betweeninnerlayers used in high frequency applications while maintainingexcellent signal integrity.

The process described herein can be used in both, horizontal andvertical process configurations. One skilled in the art would know thathorizontal and vertical process configurations may require differenttimes or temperatures to achieve the same desired result. In oneembodiment, the process described herein can be used in existinghorizontal equipment that is configured for use with oxide alternativechemistry and the composition described herein replaces such oxidealternative chemistry. In another embodiment, the process describedherein is used in a vertical configuration.

The alkali usable in the oxide coating composition may be a hydroxide,including, for example, sodium hydroxide, potassium hydroxide, orammonium hydroxide, In one embodiment, the alkali comprises sodiumhydroxide. The alkali is typically used in an amount. sufficient tomaintain the pH of the composition within the desired range. In apreferred embodiment, the concentration of the alkali in the coatingcomposition is in a range of about 1 to 50 g/L, more preferably about 5to about 20 g/L,

The oxidizing agent is chosen for its stability in the composition andis preferably sodium chlorite. The inventors have found that sodiumchlorite provides a good result due to its stability, while otheroxidizing agents such as chloryls, perchloryls, hypochlorites,chlorates, and perchlorates are generally not preferred because they arenot stable in the composition. The oxidizing agent is preferably used ata concentration within a range of about 10 to about 240 g/L, morepreferably within a range of about 70 to 180 g/L, most preferably withina range of about 140 to 150 g/L.

The acid used in the composition described herein is typically aninorganic acid. In a preferred embodiment, the acid comprises phosphoricacid due to its grain refining capability. preferred embodiment, theacid comprises phosphotic acid due to its grain refining capability. Theconcentration of the acid in the composition is preferably within arange of about 1 to about 20 g/L, more preferably about 2 to about 10g/L, and most preferably about 2.5 to about 5.0 g/L.

The corrosion inhibitor is preferably a nitrogen heterocyclic compound.In one embodiment, the nitrogen heterocyclic compound is a 5 and 6membered nitrogen heterocyclic compound which may be selected fromazoles, pyridines, pyrimidines, piperidines, and morpholines. In oneembodiment, the nitrogen heterocyclic compound is incorporated in theformulation to form an acid resistant coating on the metal conductinglayer and reduce and/or eliminate pink ring. This nitrogen heterocycliccompound is incorporated into the plating composition in an amountsufficient to bond with the oxide coating to produce an acid resistantsurface on the metal conducting layer.

While many nitrogen heterocyclic compounds attribute some sort, of acidresistance to the metal conducting layer, preferred compounds alsoresult in a good cosmetic appearance and are compatible with the otheringredients of the composition. By “good cosmetic appearance” what ismeant is a surface that is uniform in color, with no blotchy spots ordiscoloration.

The inventors have found better success with smaller inhibitors withrespect to acid resistance due in part to their ability to coordinatemore readily with the oxide structure. Based thereon, in one embodiment,the corrosion inhibitor is an unsubstituted or substituted azole.

In one embodiment, the nitrogen heterocyclic compound is unsubstitutedor substituted with a halogen substituent, where efficacy is generallyinversely proportional to the molecular weight of the halogensubstituent.

Examples of preferred azole-based inhibitors include substituted orunsubstituted pyrazoles, imidazoles, triazoles, tetrazoles, thiazoles,carbazoles, indazoles, benzimidazoles, benzotriazoles, benzothiazoles,benzoduadiazoies, and combinations of one or more of the foregoing. Inone embodiment, the azole-based inhibitor has a ring structure thatincludes a halogen substituent, which halogen substituent may be, forexample, chloride or bromide. In another embodiment, the azole-basedinhibitor is a sulfur substituted azole-based inhibitor, such as asulfur substituted benzotriazole.

Examples of suitable azole based inhibitors usable in the compositionsof the invention include, but are not limited to, imidazole,14-dichlobenzotriazole, 4,5-dichioro-2H-benzotriazole,1,4-dichlorobenzotriazole, 5,5-dichlorobenzotriazole, 56-dichlorobenzotriazole, 2,5-dichlorobenzotriazole,2,4-dichlorobenzotriazo!e, 2,6-dichlorobenzotriazole,2,7-dichlorobenzotriazole, 5-chlorobenzotriazole, 1-chlorobenzotriazole,2-chlorobenzotriazole, 2bromo-1H-indazole, 4-bromo-1H-indazole,5-bromo-1H-indazole, 6-bromo-1H-indazoIe, 7-bromo-1H- indazole,4-bromo-1H-imidazole,5-bromo-1H-imidazole-2-carboxylic acid,1,2-dibronroimidazole-d-carboxylic acid, 2,4-dibromo-1H-imidazole,4,5-dibromo-1H-imidazole, 1,4-dibromo- 1H-imidazole, 4,4-dibromo-1H-imidazole, benzimidazole, 2-4-dibromoimidazole,4,5-dichloroimidazole, 1,5-dichloromidazole, 3,4-dichloroimidazole,4,5-dichloroimidazole-1-carboxylic acid, 1 ,2-dicloroimidazole,4,5-dicbloro- 1H-imidazole, 2,2-dichloroimidazole,1,4-dichloroimidazole, 4,4-dichloroimidazole, 2,5-dichloro-1H-imidazole,benzotriazole-5-carboxlicy acid, and other similar compounds, along withcombinations of one or more of the foregoing,

While the use of azole-based corrosion inhibitors in adhesion promotingcompositions of the prior art, is described, for example, in U.S. Pat.Nos. 6,554,948, 6,419,784, and 6,146,701, all to Ferrier, these priorart compositions are designed to produce a microroughened surface. Incontrast to prior art compositions that are based on azole chemistry,the compositions of the present invention are designed not to provideany micro-roughening but rather to produce a nano oxide layer on thesurface of the metal conducting layer that exhibits a good cosmeticappearance. As such, the particular type of corrosion inhibitor and theconcentration(s) at which the corrosion inhibitors are used, along withconcentrations of the other bath constituents, are important aspects ofthe present invention.

The inventors have discovered that a critical aspect of the presentinvention is the size of the nitrogen heterocyclic compound. It hassurprisingly been found that smaller organic structures can produce agreater peel strength per unit surface area and coordinate better withthe formation of the oxide on the surface of the metal conducting layer.Thus, as set forth herein, monocyclic compounds are generally preferred.On the other hand, as the structure of the nitrogen heterocycliccompound grows in size, efficacy can be reduced.

The nitrogen heterocyclic compounds described herein are typically usedat a concentration within a range of about 1 ppb to about. 5,000 ppm,depending on the particular inhibitor, and substituents attached to thering structure, and the molecular weight of the nitrogen heterocycliccompound as well as the type and concentrations of the other bathconstituents.

The difference in concentration range employed can be attributed to theelectron donating or withdrawing properties of the substituents. As withelectronic-donating chloride substitution, it increases the strength ofthe nitrogen bond to the copper surface, thereby making the inhibitorstrong. Whereas the electron withdrawing carboxylic acid group weakensthe inhibitor leading to the use of higher concentrations. In the caseof sulfur substitution, sulfur can act as a nucleophile and lead to verystrong inhibition.

For example, benxotriazoles, including chlorobenzotriazoles, may be usedat a concentration in the range of about 25 to 300 ppm, more preferably50 to 150 ppm, most preferably 70 to 80 ppm. On the other hand,benzotriazole-5-carboxylic acid may be used at a concentration in therange of about 100 to 2,000 ppm, more preferably 500 to 1,500 ppm, mostpreferably about 900 to about 1,100 ppm, and sulfur substitutedbenzotriazoles, may suitably be used at concentrations as low as 1 ppb,such as concentrations between 1 and 50 ppb.

In one embodiment, the oxide coating composition comprises:

-   i. 1 to 50 g/L of an alkali;-   ii. 10 to 240 g/L of an oxidizing agent;-   iii. 1 to 20 g/L of an acid; and-   iv. 1 ppb to 5,000 ppm of a corrosion inhibitor, wherein the    corrosion inhibitor comprises a nitrogen heterocyclic compound as    described herein.

In a preferred embodiment, no other components are included in thecomposition described herein. In one embodiment, the present inventionconsists essentially of an alkali, an oxidizing agent, an acid, and thenitrogen heterocyclic compound at concentrations as described herein. Inanother embodiment, the present invention consists of an alkali, anoxidizing agent, an acid, and the nitrogen heterocyclic compound ,absent any unavoidable contaminants at concentrations as set forthherein. By “consisting essentially of”, what is meant is that thecomposition is free of any component that has a detrimental effect onoxide weight, adhesion promoting, edge attack, and acid resistance.

The inventors of the present invention have found that the ratio ofoxidizing agent to alkali has an effect on the oxide structure, oxidecolor, etc. and can ultimately change the performance of the oxide. Inone embodiment, the ratio of chlorite to sodium hydroxide in thecomposition, is within a range of about 1:1 to about 20:1, morepreferably about 10:1 to about 19:1, most preferably about 15:1 to about18:1.

The pH of the oxide coating composition is preferably maintained overthe Lifetime of the oxide coating composition at between about 11 toabout 15, more preferably about 12 to about 14, more preferably about12.5 to about 13.8, most preferably at about 13.1 to about 13.3. In oneembodiment, the pH of the oxide coating composition is maintained atabout 13.2 over the lifetime of the oxide coating composition. Ifadjustments are necessary,alkali and/or acid can be added to adjust thepH of the composition to within the desired range.

The temperature of the oxide coating composition is preferablymaintained at between about 40 and 80° C., more preferably between about45 and 75° C., most preferably between about 48 and about 60° C. In oneembodiment, the temperature of the oxide coating composition ismaintained at about 50° C. for both the pre-dip and the coatingsolution. The temperature of the oxide coating composition can bemaintained at this level during both horizontal and vertical processing.In addition, it is believed that a temperature within this range isoptimal for horizontal processing.

After contacting the copper surface with the oxide coating compositionto create the nano-crystalline oxide structure on the copper surface, adielectric non-conductive layer, such as a pre-preg layer, polymericphotoresist, dry film, etc., is placed directly adjacent, to the coppersurface in an adhesion step to join the copper surface to the dielectricnon-conductive layer and form a multi-layer printed circuit board. Heatand/or pressure can be used to initiate the adhesion reaction. Severallayers may be placed together in the adhesion step to laminate severallayers together in a single step.

Oxide weight is one indicator of bath performance and is evaluated bycopper weight gain coupons. It is desirable that the oxide weight behigh enough to promote excellent adhesion while at the same time beinglow enough to provide sufficient acid resistance. The oxide weight ispreferably between about 0.010 and about 0.150 mg/cm². more preferablyabout 0.015 to about 0.035 mg/cm². Below an oxide weight of about 0.025mg/cm², it is observed that acid resistance is better, while above anoxide rate of about 0.040 mg/cm², it is observed that the acid attack ismore prevalent.

The invention will now be described with reference to the followingnon-limiting examples:

EXAMPLES

The cycle set forth in Table 1 was used in processing copper foils tomanufacture 6-jayet test panels (Megtron-6 Pre-preg, available fromPanasonic) for all of these examples:

TABLE 1 Cycle for processing test panels Step Time (Minutes) MultiBondAcid Cleaner S, 43° C. 3 Cold water rinse 2 MultiBond Alkaline CleanerR, 50° C. 5 Cold water rinse 2 Predip (50° C.) 0.5 Oxide coatingcomposition, 50° C. 1 Cold water rinse 1 Forced air dry 0.5

MultiBond Acid Cleaner S and MultiBond Alkaline Cleaner R are bothavailable from MacDermid Enthone Inc., Waterbury, CT.

It is noted that all of the examples were processed vertically accordingto the steps of Table 1.

The following parameters were evaluated:

-   1) Surface roughness, minimal change to incoming copper surface-   2) Uniform cosmetic appearance-   3) Ability for the process to work on all types of copper-   4) Adhesion to various non-conductive materials (including MEG-6,    370 HR, and ABF)-   5) Thermal stability – at least 30+ cycles to delamination and 30+    minutes T-300. The cycles to delamination are processed through a    reflow over, with a reflow profile at 260° C. peak temperature. The    T-300 test is performed using a Thermal Mechanical Analyzer (TMA)    which runs isothermal at 300° C. for 60 minutes to force    delamination of the test samples.-   6) Acceptable acid resistance.

Example 1

Tests were conducted to evaluate the effectiveness of various oxidecoating compositions.

An oxide coating composition was prepared comprising:

-   6-12 g/L sodium hydroxide-   120-180 g/L sodium chlorite-   2-6 g/L phosphoric acid

A corrosion inhibitor was included in the composition as followsSolution 1: No corrosion inhibitor Solution 2: 75 ppm of benzotriazole(BTA) Solution 3: 75 ppm of 5-chlorobenzotriazole (5-Cl-BTA) Solution 4:1000 ppm of benzotriazole-5-carboxylic acid (BTA-5-COOH)

Aqueous solutions were made up by mixing the alkali, oxidizing agent,and acid together along with the listed corrosion inhibitors to produceSolutions 1 to 4. Each of Solutions 1 to 4 was then applied to thecopper foils to manufacture the 6-layer test panel.

The test foils were contacted with the aqueous solutions for a 30/60second cycle, in which the first number refers to the dwell time in thepre-dip composition and the second number refers to the dwell time inthe oxide coating composition. Thereafter, the test panels wereexamined.

FIG. 1 shows the effect of the addition of the different corrosioninhibitors on appearance as compared with the aqueous solution that didnot contain any corrosion inhibitor. As seen in FIG. 1 , the addition ofthe corrosion inhibitor results in a different oxide appearance and alsodemonstrated improved acid resistance. The adhesion data (lbs./in.) wasdetermined before and after 6X reflows and is depicted in FIG. 1 .

Table 2 shows the results of pink ring (µm) after steps of Desmear,plated through-hole processing (PTH), and acid copper and edge attack(µm) after Desmear and PTH. As seen in Table 2, the compositionscontaining the corrosion inhibitor of the invention resulted in muchsmaller amounts of both pink ring and edge attack, indicating thatbetter acid resistance was achieved.

TABLE 2 Results of pink ring and edge attack Corrosion inhibitor PinkRing (µm) Edge Attack (µm) None 81.0 90.2 BTA 51.8 40.4 5-Cl-BTA 41.436.7 BTA-5-COOH 42.1 23.4

FIG. 2 depicts a cross-section of a 6-layer test panel that includedboth MEG-6 cores and Prepreg and that was cycled through 20 cycles. Nodelamination was observed after 20 cycles for each of Solutions 2 to 4.

FIG. 3 depicts a cross-section of a 6-layer test panel that includedboth MEG-6 cores and Prepreg and that had been cycled for 30 minutes. Nodelamination was observed after 30 minutes for each of Solutions 2 to 4.

Example 2

A time study was performed to compare a test solution that did notcontain a corrosion inhibitor and a solution that contained 75 ppm ofBenzotriazole as a corrosion inhibitor and the results are shown inTable 3. Both oxide weight and peel strength were measured for differentdwell times in the test solutions. As shown in Table 3, the oxide weightat a dwell time of 30/60 seconds was much lower in the solution thatcontained the corrosion inhibitor and within the desired oxide weight.As set forth above, the first number refers to the dwell time in thepre-dip composition and the second number refers to the dwell time inthe oxide composition.

As seen in Table 3, the oxide weight at higher dwell times was muchhigher, indicating that lower dwell times provided a better result. Inaddition, peel strength was determined both as is and after 6X reflows.The peel strength is better without the organic corrosion inhibitor,both as is and after 6X reflows. With the corrosion inhibitor in theoxide bath, it coordinates with the oxide during formation of the nanocoating and slightly modifies the structure yielding slightly loweradhesion but improved acid resistance

TABLE 3 Time Study of Corrosion Inhibitor (Benzotriazole) Dwell Time(sec.) Oxide weight (mg/cm²) Peel Strength (lbs./in.) No organic 75 ppmBTA No organic 75 ppm BTA As Is 6X Reflows As Is 6X Reflows 30/60 0.05880.0340 4.85 5.00 4.60 4.35 60/120 0.0665 0.0680 4.60 5.20 4.50 4.2090/180 0.0723 0.0932 5.10 5.40 5.00 4.85 120/240 0.0743 0.0636 4.30 5.204.65 4.90

Example 3

The same study was performed using 75 ppm of 5-Chlorobenzotriazole andthe results are shown in Table 4. Both oxide weight and peel strengthwere measured for different dwell times in the test solutions. As shownin Table 4, the oxide weight at a dwell time of 30/60 seconds was muchlower in the solution that contained the corrosion inhibitor and withinthe desired oxide weight. However, the oxide weight at higher dwelltimes was much higher, indicating that lower dwell times provided abetter result. In addition, peel strength was observed both as is andafter 6X reflows.

TABLE 4 Time Study of Corrosion Inhibitor (5-Chlorobenzotriazole) DwellTime (sec.) Oxide weight (mg/cm²) Peel Strength (lbs./in.) No organic 75ppm 5-Cl-BTA No organic 75 ppm 5-Cl-BTA As Is 6X Reflows As Is 6XReflows 30/60 0.0607 0.0272 5.50 5.15 2.70 1.80 60/120 0.0694 0.06265.30 5.25 4.30 3.20 90/180 0.0684 0.0859 5.25 4.80 5.25 3.75 120/2400.0767 0.0995 5.25 5.30 5.05 5.25

Example 4

The same study was also performed using 1,000 ppm ofBenzotriazole-5-carboxylic acid and the results are shown in Table 5.Both oxide weight and peel strength were measured for different dwelltimes in the test solutions. As shown in Table 5, the oxide weight at adwell time of 30/60 and 60/120 seconds was much lower in the solutionthat contained the corrosion inhibitor and within the desired oxideweight. However, the oxide weight at higher dwell times was much higher,indicating that lower dwell times provided a better result. In addition,peel strength was observed both as is and after 6X reflows.

TABLE 5 Time Study of Corrosion Inhibitor (Benzotriazole-5-carboxylicacid) Dwell Time (sec.) Oxide weight (mg/cm²) Peel Strength (lbs./in.)No organic 1000 ppm BTA-5-COOH No organic 1000 ppm BTA-3-COOH As Is 6XReflows As Is 6X Reflows 30/60 0.0529 0.0121 5.25 4.10 0.70 0.65 60/1200.0631 0.0301 4.55 3.85 3.00 3.45 90/180 0.0680 0.1019 4.70 4.15 4.603.35 120/240 0.0723 0.0772 5.10 4.95 4.75 4.45

Example 5

A time study was performed to determine the amount of edge attack forseveral different azoles, at various dwell times. The copper foils wereprocessed through the nano oxide process and then laminated with thedesired resin system. After lamination, one-inch strips were taped offand the remaining copper was etched away to expose the laminate. Thetest samples were then processed through Desmear and PTH and then thetaped strips were pulled from the laminate. The edges of the strips wereviewed under a high magnification microscope to determine the amount ofattack on the oxide coating. The results are shown in Table 6.

A desirable edge attack value is preferably less than about 100 µm, morepreferably less than about 50 µm, more preferably less than about 40 µm,more preferably less than about 30 µm, more preferably less than about20 µm, and even more preferably less than about 15 µm.

TABLE 6 Edge Attack Dwell Time (sec.) Edge Attack (µm) No organic BTA NoOrganic 5-Cl-BTA No Organic BTA-5-COOH 30/60 71.9 34.7 56.1 25.5 13126.2 60/120 155 50.6 112 27.4 141 46.7 90/180 126 81.5 88.7 32.8 11362.0 120/240 135 126 64.3 64.6 148 60.0

FIG. 4 depicts a scatter plot of peel strength versus oxide rate forvarious organic additives. As shown in FIG. 4 , lower oxide weights wereachievable by using the corrosion inhibitors of the invention andadequate peel strength was also observed.

Example 6

A time study was performed to compare a test solution that did notcontain a corrosion inhibitor as compared with a solution that contained75 ppm of Benzotri azole as a corrosion inhibitor as described above inTable 3 but for different dwell times and the results are shown in Table7. Both oxide weight and peel strength were measured for different dwelltimes in the test solutions. As shown in Table 7, the oxide weight atdwell times of 30/60 seconds and lower were all much lower in thesolution that contained the corrosion inhibitor and within the desiredoxide weight.

TABLE 7 Time Study of Corrosion Inhibitor (Benzotriazole) Dwell Time(see.) Oxide weight (mg/cm²) Peel Strength (lbs./in.) No organic 75 ppmBTA No organic 75 ppm BTA As Is 6X Reflows As Is 6X Reflows 15/30 0.02620.04146 3.15 2.65 2.15 1.15 20/40 0.0354 0.0194 3.80 2.20 1.85 2.2025/50 0.0452 0.0238 4.65 3.05 2.95 2.05 30/60 0.0544 0.0316 4.40 3.403.45 3.25 30/60 (1^(st) test) 0.0588 0.0340 4.85 5.00 4.60 4.35

Table 8 depicts a time study of edge attack data for dwell times of15/30 to 120/240 for the benzotriazole corrosion inhibitor. As shown inTable 8, the edge attack was less at all dwell times as compared withthe solutions that did not contain an organic and the values of edgeattack were generally better at lower dwell times.

TABLE 8 Time Study of Edge Attack Dwell Time (Sec.) Edge Attack (µm) Noorganic BTA 15/30 30.8 18.4 20/40 48.8 22.3 25/50 60.1. 35.0 30/60 77.144.0 30/60 (1^(st) Test) 71.9 34.7 60/120 155 50.6 90/180 126 81.5120/240 135 126

Table 9 depicts a time study of oxide weight and adhesion (peelstrength) for dwell times of 15/30 to 30/60 for the benzotriazolecorrosion inhibitor.

TABLE 9 Time Study - Oxide Weight and Adhesion Dwell Time (sec.) OxideWeight (mg/cm²) Peel Strength (lbs./in.) As Is 6X Reflows 15/30 0.03695.00 5.00 20/40 0.0413 4.25 3.80 25/50 0.0524 4.60 4.70 30/60 (No BTA)0.0607 4.60 4.50 30/60 0.0597 4.60 4.85 M-Speed HF (30 µin) 3.30 2.90

The dwell time study shows that higher oxide weight and thickness leadsto more acid attack at the interface. The shorter dwell times (i.e.,less than 30/60 seconds) exhibited better acid resistance and edgeattack as low as 14 µm.

The BTA concentration was adjusted to optimize peel strength andcosmetic uniformity. In one embodiment, a BTA concentration of 75 ppmwas determined to produce a good result.

The present invention shows that for various nitrogen heterocycliccompounds , a dwell time of 30/60 seconds provides a good result.

Example 7

A study was performed using Imidazole as the corrosion inhibitor and theresults are provided below in Table 10 for various concentrations ofimidazole.

TABLE 10 Imidazole Concentration Study: Imidazole (ppm) Oxide Weight(mg/cm²) Edge Attack (µm) Peel Strength (lbs./in.) As Is 6X Reflows 00.0539 74.8 4.8 4.9 50 0.0427 48.6 4.9 4.6 100 0.0315 32.9 4.1. 4.1 1500.0184 13.6 3.7 3.7 M-Speed HF Control 0 3.3 3.2

As shown in FIG. 5 and as set forth in Table 10, oxide weight, edgeattack and peel strength values demonstrated good results atconcentrations of 50 and 150 ppm.

Example 8

A study was performed using Dichlorobenzotriazole as the corrosioninhibitor and the results are provided below in Table 11,

TABLE 11 Dlchlorobenzotriazole Concentration Study:Dichiorobenzotriazole (ppm) Oxide Weight (mg/cm²) Edge Attack (µm) PeelStrength (lbs./in.) As Is 6X Reflows 0 0.0563 62.1 4.2 4.7 25 0.052467.2 4.7 4.3 50 0.0383 47.2 4.4 4.5 75 0.0252 39.6 3.5 3.3 100 0.018035.4 2.5 3.0 M-Speed HF Control 0 3.2 3.2

As shown in FIG. 6 and as set forth in Table 11, oxide weight, edgeattack and peel strength values demonstrated good results atconcentrations of 25 and 50 ppm, but at a concentrations of 75 and 100ppm Dichlorobenzotriazole, the oxide weight decreased, and the peelstrength was also diminished.

Example 9

TABLE 12 4-Bromo-1H-indazole Concentration Study: 4-Bromo-1H-indazole(ppm) Oxide Weight (mg/cm²) Edge Attack (µm) Peel Strength (lbs./in.) AsIs 6X Reflows 0 0.0558 89.1 4.1 3.7 2 0.0495 69.0 4.1 2.9 4 0.0417 64.93.6 2.5 6 0.0257 50.4 3.1 1.6 M-Speed HF Control 0 3.1 3.4

As set forth in Table 12, the 4-Bromo-1H-indazole was used at a muchlower concentration than the other azoles described above. However, atconcentrations in the range of 2-6 ppm,oxide weight, edge attack andpeel strength values demonstrated good results, although, oxide weightand peel strength decreased at the higher concentration of 6 ppm.However, edge attack values were higher than for some of the other azolecorrosion inhibitors tested.

Example 10

TABLE 13 Benzimidazole Concentration Study: Benzimidazole (ppm) OxideWeight (mg/cm²) Edge Attack (pm) Peel Strength (lbs./in.) As Is 6XReflows 0 0.0524 65.7 4.7 4.6 25 0.0481 52.9 4.2 4.2 50 0.0515 63.0 1.61.9 75 0.0461 86.2 0.5 0.6 100 0.0417 79.6 <0.5 <0.5 M-Speed HF Control0 2.4 2.4

As seen in Table 13, the bath was most stable at only lowerconcentrations of benzimidazole. While oxide rate remained acceptable,the peel strength did not demonstrate good results above about 25 ppmand edge attack values were high throughout the range. Thus, whileBenzimidazole may be used as the azole corrosion inhibitor, carefulcontrol of the benzimidazole concentration and other parameters isnecessary to produce an acceptable result.

Example 11

TABLE 14 Imidazole Concentration Study: Imidazole (ppm) Oxide Weight(mg/cm²) Edge Attack (µm) Peel Strength (lbs./in.) As Is 6X Reflows 00.0544 83.1 4.5 4.8 100 0.0330 28.4 4.5 4.3 200 0.0146 8.02 2.7 2.8 4000.0078 21.0 <0.5 <0.5 M-Speed HF Control 0 3.2 3.3

As seen in Table 14, the bath shuts down at a concentration of 400 ppmimidazole. The peel strength at this concentration was less than 0.5lbs./in, due to very low oxide weight and poor oxide development.However, edge attack values were very good over the concentration range.

Example 12

TABLE 15 4-Bromo-imidazole Concentration Study: 4-Bromo-imidazole (ppm)Oxide Weight (mg/cm²) Edge Attack (µm) Peel Strength (lbs./in.) As Is 6XReflows 0 0.0510 65.8 4.5 5.0 10 0.0495 55.8 4.8 5.0 25 0.0476 70.2 4.75.1 50 0.0417 64.0 4.7 4.7 75 0.0393 55.4 4.7 4.7 100 0.0354 50.6 4.74.6 125 0.0320 47.4 4.7 4.9 150 0.0315 54.9 4.5 4.9 M-Speed HF Control 03.3 3.2

As set forth in Table 15, the bath did not shut down up to 150 ppm4~Bromoirnidazole. There was a gradual decrease in oxide weight, butexcellent peel strength was maintained. Edge attack performance heldsteady and was acceptable but not great.

A further study of 4-Bromo-imidazole was performed over a widerconcentration range and the results are shown in Table 16.

TABLE 16 4-Bromo-imidazole Concentration Study up to 400 ppm:4-bromo-imidazole (ppm) Oxide Weight (mg/cm²) Edge Attack (µm) PeelStrength (lbs./in.) As Is 6X Reflows 0 0.0582) 60.4 4.8 5.0 50 0.041746.9 4.8 4.6 100 0.0311 46.7 4.7 4.4 200 0.0248 33.1 4.8 4.6 300 0.019430.3 4.4 4.1 400 0.0180 20.6 4.5 4.1 M-Speed HF Control 0 3.3 3.6

As seen in Table 16, the bath did not shut down, even at concentrationsof 400 ppm 4∼ Bromo-imidazole. There was a continued decrease in oxideweight as the concentration increased, but the peel strength remainedexcellent. There was a significant improvment in edge concentrations,but it was observed that the cosmetic appearance exhibited a littlenon-uniformity. attack at the higher little non-uniformity.

Example 13

TABLE 17 2,4-Dibromo-imidazole Concentration Study:2,4-Dibromo-imidazole (ppm) Oxide Weight (mg/cm²) Edge Attack (µm) PeelStrength (lbs./in.) As Is 6X Reflows 0 0.0451 70.2 4.9 4.9 10 0.053956.8 4.9 5.0 25 0.0694 80.8 4.7 4.8 50 0.0544 85.5 4.8 4.9 100 0.052475.6 5.0 5.0 200 0.0500 73.0 4.5 4.8 300 0.0476 74.4 4.9 4.9 400 0.045664.3 4.6 4.3 500 0.0476 90.9 4.6 4.5 M-Speed HF Control 0 2.4 2.6

As seen in Table 17, the bath did not shut down, even at 500 ppm. Nosignificant changes in performance were observed in terms of oxideweight gain, cosmetics, edge attack, and peel strength over theconcentration range. However, the edge attack performance was relativelypoor over the concentration range.

Example 14

TABLE 18 4,5~Diehloro-imidazole Concentration Study:4,5-Dichloro-imidazole (ppm) Oxide Weight (mg/cm²) Edge Attack (µm) PeelStrength (lbs./in.) As Is 6X Reflows 0 0.0471 58.4 5.0 5.3 25 0.046682.9 4.9 5.1 50 0.0558 59.0 4.7 5.0 75 0.0544 59.0 4.9 5.1 100 0.050765.2 4.8 5.1 200 0.0485 67.8 4.9 5.1 400 0.0447 69.9 4.9 4.8 800 0.012637.7 3.2 1.6 M-Speed HF Control 0 2.9 3.0

As seen in Table 18 the bath did not shut down even at a concentrationof 800 ppm. However, the cosmetic appearance at this concentration wasunacceptable and the oxide weight and peel strength dropped offsignificantly. Throughout the concentration range up to 400 ppm, theoxide weight and peel strength remained steady. The edge attackperformance was poor as compared with other azoles.

The examples demonstrate that the type and concentration of the nitrogenheterocyclic compounds along with the dwell times are important factorsfor enhancing adhesion between metal conducting layers and inorganicmaterials using the process described herein and that a balance of thesefactors is necessary to achieve optimal results.

It is desirable that the nitrogen heterocyclic compound be used in thebath at a concentration that is capable of achieving the followingdesirable properties:

-   a. An oxide weight gain within the range of about 0.010 to about    0.080, more preferably about 0.015 to about 0.070, more preferably    about 0.015 to about 0.035, mg/cm² to provide good adhesion and acid    resistance; and/or-   b. Edge attack of less than less than about 100 µm, more preferably    less than about 50 µm, more preferably less than about 40 µm, more    preferably less than about 30 µm, more preferably less than about 20    µm, and even more preferably less than about 15 µm; and/or-   c. Peel strength of greater than about 2.0 lbs./in., more preferably    greater than about 3.0 lbs./in., more preferably greater than about    4.0 lbs./in., more preferably greater than about 4.5 lbs./in. both    as is and after 6X reflows and it is generally preferable that the    peel strength and after 6X reflows be relatively consistent.

For the best results, it is preferred that all of these properties bemet. As evidenced by the examples, the concentration of the nitrogenheterocyclic compound in the composition can vary widely depending onthe particular inhibitor being used.

Finally, it should also be understood that the following claims areintended to cover all of the generic and specific features of theinvention described herein and all statements of the scope of theinvention that, as a matter of language might fall therebetween.

What is claimed is:
 1. A process for enhancing adhesion between a metalconducting layer and an inorganic material or polymeric resin material,the process comprising the steps of: a) applying a pre-dip to the metalconducting layer; b) applying an oxide coating composition to the metalconducting layer to produce an acid resistant surface, wherein the oxidecoating composition comprises: i. an alkali; ii. an oxidizing agent:iii. an acid; and iv. a corrosion inhibitor, wherein the corrosioninhibitor comprises a nitrogen heterocyclic compound: and c) bonding theinorganic material or polymeric resin material to the metal conductinglayer.
 2. The process according to claim 1, wherein the metal conductinglayer comprises copper or a copper alloy.
 3. The process according toclaim 1, wherein the alkali of the adhesion promoting composition is ahydroxide selected from the group consisting of sodium hydroxide,potassium hydroxide, ammonium hydroxide, and combinations of one or moreof the foregoing.
 4. The process according to claim 1, wherein theoxidizing agent of the oxide coating composition comprises sodiumchlorite.
 5. The process according to claim 1, wherein the acid of theoxide coating composition comprises phosphoric acid.
 6. The processaccording to claim 5, wherein the acid consists of phosphoric acid. 7.The process according to claim 1, wherein the nitrogen heterocycliccompound is selected from the group consisting of azoles, pyridines,pyrimidines, piperidines, morpholines, and combinations of one or moreof the foregoing.
 8. The process according to claim 7, wherein thenitrogen heterocyclic compound comprises an azole-based corrosioninhibitor selected from the group consisting of unsubstituted orsubstituted pyrazoles, imidazoles, triazoles, tetrazoles, thiazoles,thiadiazoles, carbazoles, indazoles, benzimidazoles, benzotriazoles,benzothiazoles, benzothiadiazoles, and combinations of one or more ofthe foregoing.
 9. The process according to claim 8, wherein theazole-based corrosion inhibitor has a ring structure that includes ahalogen substituent.
 10. The process according to claim 8, wherein thehalogen constituent is at least one of chloride and bromide.
 11. Theprocess according to claim 1, wherein the nitrogen heterocyclic compoundis a substituted or unsubstituted monocyclic compound.
 12. The processaccording to claim 8, wherein the azole-based corrosion inhibitor isselected from the group consisting of imidazole,1,4-dichlorobenzotriazole, 4,5-dichloro-2H-benzotriazole,1,4-dichlorobenzotriazole, 5,3-dichlorobenzotriazole,5,6-dichlorobenzotriazole, 2,5-dichlorobenzotriazole,2,4-dichlorobenzotriazole, 2,6-dichlorobenzotriazole,2,7-dichlorobenzotriazole, 5-chlorobenzotriazole, 1-chlorobenzotriazole,2-chlorobenzotriazole, 2-bromo-1H-indazole, 4-bromo-1H-indazole,5-bromo-1H-indazole, 6-bromo-1H-indazole, 7-bromo-1H-indazole,4-bromo-1H-imidazole,5-bromo-1H-imidazole-2-carboxylic acid,1,2-dibromoimidazole-4-carboxylic acid, 2,4-dibromo-1H-imidazole,4,5-dibromo-1H-imidazole, 1,4-dibromo-1H-imidazole,4,4-dibromo-1H-imidazole, benzimidazole, 2-4-dibromoimidazole,4,5-dichloroimidazole, 1,5-dichloroimidazole, 3,4-dichloroimidazole,4,5-dichloroimidazole-1-carboxylic acid, 1,2-dicloroimidazole,4,5-dichloro-1H-imidazole, 2,2-dichloroimidazole, 1,4-dichloroimidazole,4,4-dichloroimidazole, 2,5-dichloro-1H-imidazole,benzotriazole-5-carboxlicy acid, and combinations of one or more of theforegoing.
 13. The process according to claim 1, wherein the of theoxide coating composition is maintained at a pH of between about 12 andabout
 14. 14. The process according to claim 1, wherein the oxidecoating composition is maintained at a temperature between about 40 andabout 80° C.
 15. The method according to claim 1, wherein the substrateis contacted with the composition for a period of 15 to 240 seconds. 16.The method according to claim 1, wherein ratio of oxidizing agent toalkali is in a range of about 1:1 to about 20:1.
 17. The methodaccording to claim 1, wherein an oxide rate on the metal conductinglayer is between about 0.010 and about 0.080 mg/cm².
 18. A multilayerwiring board prepared by the process of claim
 1. 19. The multilayerwiring board according to claim 18, wherein the multilayer wiring boardexhibits the following properties: a. an oxide rate on the metalconducting layer is between about 0.020 and about 0.080 mg/cm²; and/orb. edge attack of less than less than about 75 µm; and/or c. peelstrength of greater than about 2.0 lbs./in., as is and after 6X reflows.20. An oxide coating composition comprising: i. 1 to 150 g/L of analkali; ii. 10 to 240 g/L of an oxidizing agent; iii. 1 to 20 g/L of anacid; and iv. 1 ppb to 5,000 ppm of a corrosion inhibitor, wherein thecorrosion inhibitor comprises a nitrogen heterocyclic compound.
 21. Theoxide coating composition according to claim 20, wherein the nitrogenheterocyclic compound is selected from the group consisting of azoles,pyridines, pyrimidines, piperidines, morpholines, and combinations ofone or more of the foregoing.
 22. The oxide coating compositionaccording to claim 21, wherein the nitrogen heterocyclic compoundcomprises an azole-based corrosion inhibitor selected from the groupconsisting of unsubstituted or substituted pyrazoles, imidazoles,triazoles, tetrazoles, thiazoles, thiadiazoles, carbazoles, indazoles,benzimidazoles, benzotriazoles, benzothiazoles, benzothiadiazoles, andcombinations of one or more of the foregoing.
 23. The oxide coatingcomposition according to claim 20, wherein the nitrogen heterocycliccompound has a ring structure that includes a halogen substituent. 24.The oxide coating composition according to claim 23, wherein the halogenconstituent is at least one of chloride and bromide.
 25. The oxidecoating composition according to claim 22, wherein the azote-basedcorrosion inhibitor is selected from the group consisting of imidazole,1,4-dichlorobenzotriazole, 4,5-dichloro-2H-benzotriazole,1,4-dichlorobenzotriazole, 5,5-dichlorobenzotriazole,5,6-dichlorobenzotriazole, 2,5-dichlorobenzotriazole,2,4-dichlorobenzotriazole, 2,6-dichlorobenzotriazole,2,7-dichlorobenzotriazole, 5-chlorobenzotriazole, 1-chlorobenzotriazole,2-chlorobenzotriazole, 2-bromo-1H-indazole, 4-bromo-1H-indazole,5-bromo-1H-indazole, 6-bromo-1H-indazole, 7-bromo-1H-indazole,4-bromo-1H-imidazole,5-bromo-1H-imidazole-2-carboxylic acid,1,2-dibromoimidazole-4-carboxylic acid, 2,4-dibromo-1H-imidazole,4,5-dibromo-1H-imidazole, 1,4-dibromo-1H-imidazole,4,4-dibromo-1H-imidazole, benzimidazole, 2-4-dibromoimidazole,4,5-dichloroimidazole, 1,5-dichloroimidazole, 3,4-dichloroimidazole,4,5-dichloroimidazoie-1-carboxylic acid, 1,2-dicloroimidazole,4,5-dichloro-1H-imidazole, 2,2-dichloroimidazole, 1,4-dichloroimidazole,4,4-dichloroimidazole, 2,5-dichloro-1H-imidazole,benzotriazole-5-carboxlicy acid, and combinations of one or more of theforegoing.
 26. The oxide coating composition according to claim 20,wherein the pH of the oxide coating composition is between about 12 andabout
 14. 27. The oxide coating composition according to claim 20,wherein ratio of oxidizing agent to alkali is in a range of about 1:1 toabout 20:1.